linux/fs/splice.c
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   1/*
   2 * "splice": joining two ropes together by interweaving their strands.
   3 *
   4 * This is the "extended pipe" functionality, where a pipe is used as
   5 * an arbitrary in-memory buffer. Think of a pipe as a small kernel
   6 * buffer that you can use to transfer data from one end to the other.
   7 *
   8 * The traditional unix read/write is extended with a "splice()" operation
   9 * that transfers data buffers to or from a pipe buffer.
  10 *
  11 * Named by Larry McVoy, original implementation from Linus, extended by
  12 * Jens to support splicing to files, network, direct splicing, etc and
  13 * fixing lots of bugs.
  14 *
  15 * Copyright (C) 2005-2006 Jens Axboe <axboe@kernel.dk>
  16 * Copyright (C) 2005-2006 Linus Torvalds <torvalds@osdl.org>
  17 * Copyright (C) 2006 Ingo Molnar <mingo@elte.hu>
  18 *
  19 */
  20#include <linux/fs.h>
  21#include <linux/file.h>
  22#include <linux/pagemap.h>
  23#include <linux/splice.h>
  24#include <linux/memcontrol.h>
  25#include <linux/mm_inline.h>
  26#include <linux/swap.h>
  27#include <linux/writeback.h>
  28#include <linux/module.h>
  29#include <linux/syscalls.h>
  30#include <linux/uio.h>
  31#include <linux/security.h>
  32#include <linux/gfp.h>
  33
  34/*
  35 * Attempt to steal a page from a pipe buffer. This should perhaps go into
  36 * a vm helper function, it's already simplified quite a bit by the
  37 * addition of remove_mapping(). If success is returned, the caller may
  38 * attempt to reuse this page for another destination.
  39 */
  40static int page_cache_pipe_buf_steal(struct pipe_inode_info *pipe,
  41                                     struct pipe_buffer *buf)
  42{
  43        struct page *page = buf->page;
  44        struct address_space *mapping;
  45
  46        lock_page(page);
  47
  48        mapping = page_mapping(page);
  49        if (mapping) {
  50                WARN_ON(!PageUptodate(page));
  51
  52                /*
  53                 * At least for ext2 with nobh option, we need to wait on
  54                 * writeback completing on this page, since we'll remove it
  55                 * from the pagecache.  Otherwise truncate wont wait on the
  56                 * page, allowing the disk blocks to be reused by someone else
  57                 * before we actually wrote our data to them. fs corruption
  58                 * ensues.
  59                 */
  60                wait_on_page_writeback(page);
  61
  62                if (page_has_private(page) &&
  63                    !try_to_release_page(page, GFP_KERNEL))
  64                        goto out_unlock;
  65
  66                /*
  67                 * If we succeeded in removing the mapping, set LRU flag
  68                 * and return good.
  69                 */
  70                if (remove_mapping(mapping, page)) {
  71                        buf->flags |= PIPE_BUF_FLAG_LRU;
  72                        return 0;
  73                }
  74        }
  75
  76        /*
  77         * Raced with truncate or failed to remove page from current
  78         * address space, unlock and return failure.
  79         */
  80out_unlock:
  81        unlock_page(page);
  82        return 1;
  83}
  84
  85static void page_cache_pipe_buf_release(struct pipe_inode_info *pipe,
  86                                        struct pipe_buffer *buf)
  87{
  88        page_cache_release(buf->page);
  89        buf->flags &= ~PIPE_BUF_FLAG_LRU;
  90}
  91
  92/*
  93 * Check whether the contents of buf is OK to access. Since the content
  94 * is a page cache page, IO may be in flight.
  95 */
  96static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
  97                                       struct pipe_buffer *buf)
  98{
  99        struct page *page = buf->page;
 100        int err;
 101
 102        if (!PageUptodate(page)) {
 103                lock_page(page);
 104
 105                /*
 106                 * Page got truncated/unhashed. This will cause a 0-byte
 107                 * splice, if this is the first page.
 108                 */
 109                if (!page->mapping) {
 110                        err = -ENODATA;
 111                        goto error;
 112                }
 113
 114                /*
 115                 * Uh oh, read-error from disk.
 116                 */
 117                if (!PageUptodate(page)) {
 118                        err = -EIO;
 119                        goto error;
 120                }
 121
 122                /*
 123                 * Page is ok afterall, we are done.
 124                 */
 125                unlock_page(page);
 126        }
 127
 128        return 0;
 129error:
 130        unlock_page(page);
 131        return err;
 132}
 133
 134const struct pipe_buf_operations page_cache_pipe_buf_ops = {
 135        .can_merge = 0,
 136        .map = generic_pipe_buf_map,
 137        .unmap = generic_pipe_buf_unmap,
 138        .confirm = page_cache_pipe_buf_confirm,
 139        .release = page_cache_pipe_buf_release,
 140        .steal = page_cache_pipe_buf_steal,
 141        .get = generic_pipe_buf_get,
 142};
 143
 144static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
 145                                    struct pipe_buffer *buf)
 146{
 147        if (!(buf->flags & PIPE_BUF_FLAG_GIFT))
 148                return 1;
 149
 150        buf->flags |= PIPE_BUF_FLAG_LRU;
 151        return generic_pipe_buf_steal(pipe, buf);
 152}
 153
 154static const struct pipe_buf_operations user_page_pipe_buf_ops = {
 155        .can_merge = 0,
 156        .map = generic_pipe_buf_map,
 157        .unmap = generic_pipe_buf_unmap,
 158        .confirm = generic_pipe_buf_confirm,
 159        .release = page_cache_pipe_buf_release,
 160        .steal = user_page_pipe_buf_steal,
 161        .get = generic_pipe_buf_get,
 162};
 163
 164static void wakeup_pipe_readers(struct pipe_inode_info *pipe)
 165{
 166        smp_mb();
 167        if (waitqueue_active(&pipe->wait))
 168                wake_up_interruptible(&pipe->wait);
 169        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 170}
 171
 172/**
 173 * splice_to_pipe - fill passed data into a pipe
 174 * @pipe:       pipe to fill
 175 * @spd:        data to fill
 176 *
 177 * Description:
 178 *    @spd contains a map of pages and len/offset tuples, along with
 179 *    the struct pipe_buf_operations associated with these pages. This
 180 *    function will link that data to the pipe.
 181 *
 182 */
 183ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 184                       struct splice_pipe_desc *spd)
 185{
 186        unsigned int spd_pages = spd->nr_pages;
 187        int ret, do_wakeup, page_nr;
 188
 189        ret = 0;
 190        do_wakeup = 0;
 191        page_nr = 0;
 192
 193        pipe_lock(pipe);
 194
 195        for (;;) {
 196                if (!pipe->readers) {
 197                        send_sig(SIGPIPE, current, 0);
 198                        if (!ret)
 199                                ret = -EPIPE;
 200                        break;
 201                }
 202
 203                if (pipe->nrbufs < pipe->buffers) {
 204                        int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
 205                        struct pipe_buffer *buf = pipe->bufs + newbuf;
 206
 207                        buf->page = spd->pages[page_nr];
 208                        buf->offset = spd->partial[page_nr].offset;
 209                        buf->len = spd->partial[page_nr].len;
 210                        buf->private = spd->partial[page_nr].private;
 211                        buf->ops = spd->ops;
 212                        if (spd->flags & SPLICE_F_GIFT)
 213                                buf->flags |= PIPE_BUF_FLAG_GIFT;
 214
 215                        pipe->nrbufs++;
 216                        page_nr++;
 217                        ret += buf->len;
 218
 219                        if (pipe->inode)
 220                                do_wakeup = 1;
 221
 222                        if (!--spd->nr_pages)
 223                                break;
 224                        if (pipe->nrbufs < pipe->buffers)
 225                                continue;
 226
 227                        break;
 228                }
 229
 230                if (spd->flags & SPLICE_F_NONBLOCK) {
 231                        if (!ret)
 232                                ret = -EAGAIN;
 233                        break;
 234                }
 235
 236                if (signal_pending(current)) {
 237                        if (!ret)
 238                                ret = -ERESTARTSYS;
 239                        break;
 240                }
 241
 242                if (do_wakeup) {
 243                        smp_mb();
 244                        if (waitqueue_active(&pipe->wait))
 245                                wake_up_interruptible_sync(&pipe->wait);
 246                        kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
 247                        do_wakeup = 0;
 248                }
 249
 250                pipe->waiting_writers++;
 251                pipe_wait(pipe);
 252                pipe->waiting_writers--;
 253        }
 254
 255        pipe_unlock(pipe);
 256
 257        if (do_wakeup)
 258                wakeup_pipe_readers(pipe);
 259
 260        while (page_nr < spd_pages)
 261                spd->spd_release(spd, page_nr++);
 262
 263        return ret;
 264}
 265
 266void spd_release_page(struct splice_pipe_desc *spd, unsigned int i)
 267{
 268        page_cache_release(spd->pages[i]);
 269}
 270
 271/*
 272 * Check if we need to grow the arrays holding pages and partial page
 273 * descriptions.
 274 */
 275int splice_grow_spd(struct pipe_inode_info *pipe, struct splice_pipe_desc *spd)
 276{
 277        if (pipe->buffers <= PIPE_DEF_BUFFERS)
 278                return 0;
 279
 280        spd->pages = kmalloc(pipe->buffers * sizeof(struct page *), GFP_KERNEL);
 281        spd->partial = kmalloc(pipe->buffers * sizeof(struct partial_page), GFP_KERNEL);
 282
 283        if (spd->pages && spd->partial)
 284                return 0;
 285
 286        kfree(spd->pages);
 287        kfree(spd->partial);
 288        return -ENOMEM;
 289}
 290
 291void splice_shrink_spd(struct pipe_inode_info *pipe,
 292                       struct splice_pipe_desc *spd)
 293{
 294        if (pipe->buffers <= PIPE_DEF_BUFFERS)
 295                return;
 296
 297        kfree(spd->pages);
 298        kfree(spd->partial);
 299}
 300
 301static int
 302__generic_file_splice_read(struct file *in, loff_t *ppos,
 303                           struct pipe_inode_info *pipe, size_t len,
 304                           unsigned int flags)
 305{
 306        struct address_space *mapping = in->f_mapping;
 307        unsigned int loff, nr_pages, req_pages;
 308        struct page *pages[PIPE_DEF_BUFFERS];
 309        struct partial_page partial[PIPE_DEF_BUFFERS];
 310        struct page *page;
 311        pgoff_t index, end_index;
 312        loff_t isize;
 313        int error, page_nr;
 314        struct splice_pipe_desc spd = {
 315                .pages = pages,
 316                .partial = partial,
 317                .flags = flags,
 318                .ops = &page_cache_pipe_buf_ops,
 319                .spd_release = spd_release_page,
 320        };
 321
 322        if (splice_grow_spd(pipe, &spd))
 323                return -ENOMEM;
 324
 325        index = *ppos >> PAGE_CACHE_SHIFT;
 326        loff = *ppos & ~PAGE_CACHE_MASK;
 327        req_pages = (len + loff + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 328        nr_pages = min(req_pages, pipe->buffers);
 329
 330        /*
 331         * Lookup the (hopefully) full range of pages we need.
 332         */
 333        spd.nr_pages = find_get_pages_contig(mapping, index, nr_pages, spd.pages);
 334        index += spd.nr_pages;
 335
 336        /*
 337         * If find_get_pages_contig() returned fewer pages than we needed,
 338         * readahead/allocate the rest and fill in the holes.
 339         */
 340        if (spd.nr_pages < nr_pages)
 341                page_cache_sync_readahead(mapping, &in->f_ra, in,
 342                                index, req_pages - spd.nr_pages);
 343
 344        error = 0;
 345        while (spd.nr_pages < nr_pages) {
 346                /*
 347                 * Page could be there, find_get_pages_contig() breaks on
 348                 * the first hole.
 349                 */
 350                page = find_get_page(mapping, index);
 351                if (!page) {
 352                        /*
 353                         * page didn't exist, allocate one.
 354                         */
 355                        page = page_cache_alloc_cold(mapping);
 356                        if (!page)
 357                                break;
 358
 359                        error = add_to_page_cache_lru(page, mapping, index,
 360                                                GFP_KERNEL);
 361                        if (unlikely(error)) {
 362                                page_cache_release(page);
 363                                if (error == -EEXIST)
 364                                        continue;
 365                                break;
 366                        }
 367                        /*
 368                         * add_to_page_cache() locks the page, unlock it
 369                         * to avoid convoluting the logic below even more.
 370                         */
 371                        unlock_page(page);
 372                }
 373
 374                spd.pages[spd.nr_pages++] = page;
 375                index++;
 376        }
 377
 378        /*
 379         * Now loop over the map and see if we need to start IO on any
 380         * pages, fill in the partial map, etc.
 381         */
 382        index = *ppos >> PAGE_CACHE_SHIFT;
 383        nr_pages = spd.nr_pages;
 384        spd.nr_pages = 0;
 385        for (page_nr = 0; page_nr < nr_pages; page_nr++) {
 386                unsigned int this_len;
 387
 388                if (!len)
 389                        break;
 390
 391                /*
 392                 * this_len is the max we'll use from this page
 393                 */
 394                this_len = min_t(unsigned long, len, PAGE_CACHE_SIZE - loff);
 395                page = spd.pages[page_nr];
 396
 397                if (PageReadahead(page))
 398                        page_cache_async_readahead(mapping, &in->f_ra, in,
 399                                        page, index, req_pages - page_nr);
 400
 401                /*
 402                 * If the page isn't uptodate, we may need to start io on it
 403                 */
 404                if (!PageUptodate(page)) {
 405                        lock_page(page);
 406
 407                        /*
 408                         * Page was truncated, or invalidated by the
 409                         * filesystem.  Redo the find/create, but this time the
 410                         * page is kept locked, so there's no chance of another
 411                         * race with truncate/invalidate.
 412                         */
 413                        if (!page->mapping) {
 414                                unlock_page(page);
 415                                page = find_or_create_page(mapping, index,
 416                                                mapping_gfp_mask(mapping));
 417
 418                                if (!page) {
 419                                        error = -ENOMEM;
 420                                        break;
 421                                }
 422                                page_cache_release(spd.pages[page_nr]);
 423                                spd.pages[page_nr] = page;
 424                        }
 425                        /*
 426                         * page was already under io and is now done, great
 427                         */
 428                        if (PageUptodate(page)) {
 429                                unlock_page(page);
 430                                goto fill_it;
 431                        }
 432
 433                        /*
 434                         * need to read in the page
 435                         */
 436                        error = mapping->a_ops->readpage(in, page);
 437                        if (unlikely(error)) {
 438                                /*
 439                                 * We really should re-lookup the page here,
 440                                 * but it complicates things a lot. Instead
 441                                 * lets just do what we already stored, and
 442                                 * we'll get it the next time we are called.
 443                                 */
 444                                if (error == AOP_TRUNCATED_PAGE)
 445                                        error = 0;
 446
 447                                break;
 448                        }
 449                }
 450fill_it:
 451                /*
 452                 * i_size must be checked after PageUptodate.
 453                 */
 454                isize = i_size_read(mapping->host);
 455                end_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 456                if (unlikely(!isize || index > end_index))
 457                        break;
 458
 459                /*
 460                 * if this is the last page, see if we need to shrink
 461                 * the length and stop
 462                 */
 463                if (end_index == index) {
 464                        unsigned int plen;
 465
 466                        /*
 467                         * max good bytes in this page
 468                         */
 469                        plen = ((isize - 1) & ~PAGE_CACHE_MASK) + 1;
 470                        if (plen <= loff)
 471                                break;
 472
 473                        /*
 474                         * force quit after adding this page
 475                         */
 476                        this_len = min(this_len, plen - loff);
 477                        len = this_len;
 478                }
 479
 480                spd.partial[page_nr].offset = loff;
 481                spd.partial[page_nr].len = this_len;
 482                len -= this_len;
 483                loff = 0;
 484                spd.nr_pages++;
 485                index++;
 486        }
 487
 488        /*
 489         * Release any pages at the end, if we quit early. 'page_nr' is how far
 490         * we got, 'nr_pages' is how many pages are in the map.
 491         */
 492        while (page_nr < nr_pages)
 493                page_cache_release(spd.pages[page_nr++]);
 494        in->f_ra.prev_pos = (loff_t)index << PAGE_CACHE_SHIFT;
 495
 496        if (spd.nr_pages)
 497                error = splice_to_pipe(pipe, &spd);
 498
 499        splice_shrink_spd(pipe, &spd);
 500        return error;
 501}
 502
 503/**
 504 * generic_file_splice_read - splice data from file to a pipe
 505 * @in:         file to splice from
 506 * @ppos:       position in @in
 507 * @pipe:       pipe to splice to
 508 * @len:        number of bytes to splice
 509 * @flags:      splice modifier flags
 510 *
 511 * Description:
 512 *    Will read pages from given file and fill them into a pipe. Can be
 513 *    used as long as the address_space operations for the source implements
 514 *    a readpage() hook.
 515 *
 516 */
 517ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 518                                 struct pipe_inode_info *pipe, size_t len,
 519                                 unsigned int flags)
 520{
 521        loff_t isize, left;
 522        int ret;
 523
 524        isize = i_size_read(in->f_mapping->host);
 525        if (unlikely(*ppos >= isize))
 526                return 0;
 527
 528        left = isize - *ppos;
 529        if (unlikely(left < len))
 530                len = left;
 531
 532        ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 533        if (ret > 0) {
 534                *ppos += ret;
 535                file_accessed(in);
 536        }
 537
 538        return ret;
 539}
 540EXPORT_SYMBOL(generic_file_splice_read);
 541
 542static const struct pipe_buf_operations default_pipe_buf_ops = {
 543        .can_merge = 0,
 544        .map = generic_pipe_buf_map,
 545        .unmap = generic_pipe_buf_unmap,
 546        .confirm = generic_pipe_buf_confirm,
 547        .release = generic_pipe_buf_release,
 548        .steal = generic_pipe_buf_steal,
 549        .get = generic_pipe_buf_get,
 550};
 551
 552static ssize_t kernel_readv(struct file *file, const struct iovec *vec,
 553                            unsigned long vlen, loff_t offset)
 554{
 555        mm_segment_t old_fs;
 556        loff_t pos = offset;
 557        ssize_t res;
 558
 559        old_fs = get_fs();
 560        set_fs(get_ds());
 561        /* The cast to a user pointer is valid due to the set_fs() */
 562        res = vfs_readv(file, (const struct iovec __user *)vec, vlen, &pos);
 563        set_fs(old_fs);
 564
 565        return res;
 566}
 567
 568static ssize_t kernel_write(struct file *file, const char *buf, size_t count,
 569                            loff_t pos)
 570{
 571        mm_segment_t old_fs;
 572        ssize_t res;
 573
 574        old_fs = get_fs();
 575        set_fs(get_ds());
 576        /* The cast to a user pointer is valid due to the set_fs() */
 577        res = vfs_write(file, (const char __user *)buf, count, &pos);
 578        set_fs(old_fs);
 579
 580        return res;
 581}
 582
 583ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
 584                                 struct pipe_inode_info *pipe, size_t len,
 585                                 unsigned int flags)
 586{
 587        unsigned int nr_pages;
 588        unsigned int nr_freed;
 589        size_t offset;
 590        struct page *pages[PIPE_DEF_BUFFERS];
 591        struct partial_page partial[PIPE_DEF_BUFFERS];
 592        struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
 593        ssize_t res;
 594        size_t this_len;
 595        int error;
 596        int i;
 597        struct splice_pipe_desc spd = {
 598                .pages = pages,
 599                .partial = partial,
 600                .flags = flags,
 601                .ops = &default_pipe_buf_ops,
 602                .spd_release = spd_release_page,
 603        };
 604
 605        if (splice_grow_spd(pipe, &spd))
 606                return -ENOMEM;
 607
 608        res = -ENOMEM;
 609        vec = __vec;
 610        if (pipe->buffers > PIPE_DEF_BUFFERS) {
 611                vec = kmalloc(pipe->buffers * sizeof(struct iovec), GFP_KERNEL);
 612                if (!vec)
 613                        goto shrink_ret;
 614        }
 615
 616        offset = *ppos & ~PAGE_CACHE_MASK;
 617        nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 618
 619        for (i = 0; i < nr_pages && i < pipe->buffers && len; i++) {
 620                struct page *page;
 621
 622                page = alloc_page(GFP_USER);
 623                error = -ENOMEM;
 624                if (!page)
 625                        goto err;
 626
 627                this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
 628                vec[i].iov_base = (void __user *) page_address(page);
 629                vec[i].iov_len = this_len;
 630                spd.pages[i] = page;
 631                spd.nr_pages++;
 632                len -= this_len;
 633                offset = 0;
 634        }
 635
 636        res = kernel_readv(in, vec, spd.nr_pages, *ppos);
 637        if (res < 0) {
 638                error = res;
 639                goto err;
 640        }
 641
 642        error = 0;
 643        if (!res)
 644                goto err;
 645
 646        nr_freed = 0;
 647        for (i = 0; i < spd.nr_pages; i++) {
 648                this_len = min_t(size_t, vec[i].iov_len, res);
 649                spd.partial[i].offset = 0;
 650                spd.partial[i].len = this_len;
 651                if (!this_len) {
 652                        __free_page(spd.pages[i]);
 653                        spd.pages[i] = NULL;
 654                        nr_freed++;
 655                }
 656                res -= this_len;
 657        }
 658        spd.nr_pages -= nr_freed;
 659
 660        res = splice_to_pipe(pipe, &spd);
 661        if (res > 0)
 662                *ppos += res;
 663
 664shrink_ret:
 665        if (vec != __vec)
 666                kfree(vec);
 667        splice_shrink_spd(pipe, &spd);
 668        return res;
 669
 670err:
 671        for (i = 0; i < spd.nr_pages; i++)
 672                __free_page(spd.pages[i]);
 673
 674        res = error;
 675        goto shrink_ret;
 676}
 677EXPORT_SYMBOL(default_file_splice_read);
 678
 679/*
 680 * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
 681 * using sendpage(). Return the number of bytes sent.
 682 */
 683static int pipe_to_sendpage(struct pipe_inode_info *pipe,
 684                            struct pipe_buffer *buf, struct splice_desc *sd)
 685{
 686        struct file *file = sd->u.file;
 687        loff_t pos = sd->pos;
 688        int more;
 689
 690        if (!likely(file->f_op && file->f_op->sendpage))
 691                return -EINVAL;
 692
 693        more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 694        return file->f_op->sendpage(file, buf->page, buf->offset,
 695                                    sd->len, &pos, more);
 696}
 697
 698/*
 699 * This is a little more tricky than the file -> pipe splicing. There are
 700 * basically three cases:
 701 *
 702 *      - Destination page already exists in the address space and there
 703 *        are users of it. For that case we have no other option that
 704 *        copying the data. Tough luck.
 705 *      - Destination page already exists in the address space, but there
 706 *        are no users of it. Make sure it's uptodate, then drop it. Fall
 707 *        through to last case.
 708 *      - Destination page does not exist, we can add the pipe page to
 709 *        the page cache and avoid the copy.
 710 *
 711 * If asked to move pages to the output file (SPLICE_F_MOVE is set in
 712 * sd->flags), we attempt to migrate pages from the pipe to the output
 713 * file address space page cache. This is possible if no one else has
 714 * the pipe page referenced outside of the pipe and page cache. If
 715 * SPLICE_F_MOVE isn't set, or we cannot move the page, we simply create
 716 * a new page in the output file page cache and fill/dirty that.
 717 */
 718int pipe_to_file(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
 719                 struct splice_desc *sd)
 720{
 721        struct file *file = sd->u.file;
 722        struct address_space *mapping = file->f_mapping;
 723        unsigned int offset, this_len;
 724        struct page *page;
 725        void *fsdata;
 726        int ret;
 727
 728        offset = sd->pos & ~PAGE_CACHE_MASK;
 729
 730        this_len = sd->len;
 731        if (this_len + offset > PAGE_CACHE_SIZE)
 732                this_len = PAGE_CACHE_SIZE - offset;
 733
 734        ret = pagecache_write_begin(file, mapping, sd->pos, this_len,
 735                                AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
 736        if (unlikely(ret))
 737                goto out;
 738
 739        if (buf->page != page) {
 740                /*
 741                 * Careful, ->map() uses KM_USER0!
 742                 */
 743                char *src = buf->ops->map(pipe, buf, 1);
 744                char *dst = kmap_atomic(page, KM_USER1);
 745
 746                memcpy(dst + offset, src + buf->offset, this_len);
 747                flush_dcache_page(page);
 748                kunmap_atomic(dst, KM_USER1);
 749                buf->ops->unmap(pipe, buf, src);
 750        }
 751        ret = pagecache_write_end(file, mapping, sd->pos, this_len, this_len,
 752                                page, fsdata);
 753out:
 754        return ret;
 755}
 756EXPORT_SYMBOL(pipe_to_file);
 757
 758static void wakeup_pipe_writers(struct pipe_inode_info *pipe)
 759{
 760        smp_mb();
 761        if (waitqueue_active(&pipe->wait))
 762                wake_up_interruptible(&pipe->wait);
 763        kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
 764}
 765
 766/**
 767 * splice_from_pipe_feed - feed available data from a pipe to a file
 768 * @pipe:       pipe to splice from
 769 * @sd:         information to @actor
 770 * @actor:      handler that splices the data
 771 *
 772 * Description:
 773 *    This function loops over the pipe and calls @actor to do the
 774 *    actual moving of a single struct pipe_buffer to the desired
 775 *    destination.  It returns when there's no more buffers left in
 776 *    the pipe or if the requested number of bytes (@sd->total_len)
 777 *    have been copied.  It returns a positive number (one) if the
 778 *    pipe needs to be filled with more data, zero if the required
 779 *    number of bytes have been copied and -errno on error.
 780 *
 781 *    This, together with splice_from_pipe_{begin,end,next}, may be
 782 *    used to implement the functionality of __splice_from_pipe() when
 783 *    locking is required around copying the pipe buffers to the
 784 *    destination.
 785 */
 786int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_desc *sd,
 787                          splice_actor *actor)
 788{
 789        int ret;
 790
 791        while (pipe->nrbufs) {
 792                struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 793                const struct pipe_buf_operations *ops = buf->ops;
 794
 795                sd->len = buf->len;
 796                if (sd->len > sd->total_len)
 797                        sd->len = sd->total_len;
 798
 799                ret = buf->ops->confirm(pipe, buf);
 800                if (unlikely(ret)) {
 801                        if (ret == -ENODATA)
 802                                ret = 0;
 803                        return ret;
 804                }
 805
 806                ret = actor(pipe, buf, sd);
 807                if (ret <= 0)
 808                        return ret;
 809
 810                buf->offset += ret;
 811                buf->len -= ret;
 812
 813                sd->num_spliced += ret;
 814                sd->len -= ret;
 815                sd->pos += ret;
 816                sd->total_len -= ret;
 817
 818                if (!buf->len) {
 819                        buf->ops = NULL;
 820                        ops->release(pipe, buf);
 821                        pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
 822                        pipe->nrbufs--;
 823                        if (pipe->inode)
 824                                sd->need_wakeup = true;
 825                }
 826
 827                if (!sd->total_len)
 828                        return 0;
 829        }
 830
 831        return 1;
 832}
 833EXPORT_SYMBOL(splice_from_pipe_feed);
 834
 835/**
 836 * splice_from_pipe_next - wait for some data to splice from
 837 * @pipe:       pipe to splice from
 838 * @sd:         information about the splice operation
 839 *
 840 * Description:
 841 *    This function will wait for some data and return a positive
 842 *    value (one) if pipe buffers are available.  It will return zero
 843 *    or -errno if no more data needs to be spliced.
 844 */
 845int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd)
 846{
 847        while (!pipe->nrbufs) {
 848                if (!pipe->writers)
 849                        return 0;
 850
 851                if (!pipe->waiting_writers && sd->num_spliced)
 852                        return 0;
 853
 854                if (sd->flags & SPLICE_F_NONBLOCK)
 855                        return -EAGAIN;
 856
 857                if (signal_pending(current))
 858                        return -ERESTARTSYS;
 859
 860                if (sd->need_wakeup) {
 861                        wakeup_pipe_writers(pipe);
 862                        sd->need_wakeup = false;
 863                }
 864
 865                pipe_wait(pipe);
 866        }
 867
 868        return 1;
 869}
 870EXPORT_SYMBOL(splice_from_pipe_next);
 871
 872/**
 873 * splice_from_pipe_begin - start splicing from pipe
 874 * @sd:         information about the splice operation
 875 *
 876 * Description:
 877 *    This function should be called before a loop containing
 878 *    splice_from_pipe_next() and splice_from_pipe_feed() to
 879 *    initialize the necessary fields of @sd.
 880 */
 881void splice_from_pipe_begin(struct splice_desc *sd)
 882{
 883        sd->num_spliced = 0;
 884        sd->need_wakeup = false;
 885}
 886EXPORT_SYMBOL(splice_from_pipe_begin);
 887
 888/**
 889 * splice_from_pipe_end - finish splicing from pipe
 890 * @pipe:       pipe to splice from
 891 * @sd:         information about the splice operation
 892 *
 893 * Description:
 894 *    This function will wake up pipe writers if necessary.  It should
 895 *    be called after a loop containing splice_from_pipe_next() and
 896 *    splice_from_pipe_feed().
 897 */
 898void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_desc *sd)
 899{
 900        if (sd->need_wakeup)
 901                wakeup_pipe_writers(pipe);
 902}
 903EXPORT_SYMBOL(splice_from_pipe_end);
 904
 905/**
 906 * __splice_from_pipe - splice data from a pipe to given actor
 907 * @pipe:       pipe to splice from
 908 * @sd:         information to @actor
 909 * @actor:      handler that splices the data
 910 *
 911 * Description:
 912 *    This function does little more than loop over the pipe and call
 913 *    @actor to do the actual moving of a single struct pipe_buffer to
 914 *    the desired destination. See pipe_to_file, pipe_to_sendpage, or
 915 *    pipe_to_user.
 916 *
 917 */
 918ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 919                           splice_actor *actor)
 920{
 921        int ret;
 922
 923        splice_from_pipe_begin(sd);
 924        do {
 925                ret = splice_from_pipe_next(pipe, sd);
 926                if (ret > 0)
 927                        ret = splice_from_pipe_feed(pipe, sd, actor);
 928        } while (ret > 0);
 929        splice_from_pipe_end(pipe, sd);
 930
 931        return sd->num_spliced ? sd->num_spliced : ret;
 932}
 933EXPORT_SYMBOL(__splice_from_pipe);
 934
 935/**
 936 * splice_from_pipe - splice data from a pipe to a file
 937 * @pipe:       pipe to splice from
 938 * @out:        file to splice to
 939 * @ppos:       position in @out
 940 * @len:        how many bytes to splice
 941 * @flags:      splice modifier flags
 942 * @actor:      handler that splices the data
 943 *
 944 * Description:
 945 *    See __splice_from_pipe. This function locks the pipe inode,
 946 *    otherwise it's identical to __splice_from_pipe().
 947 *
 948 */
 949ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 950                         loff_t *ppos, size_t len, unsigned int flags,
 951                         splice_actor *actor)
 952{
 953        ssize_t ret;
 954        struct splice_desc sd = {
 955                .total_len = len,
 956                .flags = flags,
 957                .pos = *ppos,
 958                .u.file = out,
 959        };
 960
 961        pipe_lock(pipe);
 962        ret = __splice_from_pipe(pipe, &sd, actor);
 963        pipe_unlock(pipe);
 964
 965        return ret;
 966}
 967
 968/**
 969 * generic_file_splice_write - splice data from a pipe to a file
 970 * @pipe:       pipe info
 971 * @out:        file to write to
 972 * @ppos:       position in @out
 973 * @len:        number of bytes to splice
 974 * @flags:      splice modifier flags
 975 *
 976 * Description:
 977 *    Will either move or copy pages (determined by @flags options) from
 978 *    the given pipe inode to the given file.
 979 *
 980 */
 981ssize_t
 982generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
 983                          loff_t *ppos, size_t len, unsigned int flags)
 984{
 985        struct address_space *mapping = out->f_mapping;
 986        struct inode *inode = mapping->host;
 987        struct splice_desc sd = {
 988                .total_len = len,
 989                .flags = flags,
 990                .pos = *ppos,
 991                .u.file = out,
 992        };
 993        ssize_t ret;
 994
 995        pipe_lock(pipe);
 996
 997        splice_from_pipe_begin(&sd);
 998        do {
 999                ret = splice_from_pipe_next(pipe, &sd);
1000                if (ret <= 0)
1001                        break;
1002
1003                mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD);
1004                ret = file_remove_suid(out);
1005                if (!ret) {
1006                        file_update_time(out);
1007                        ret = splice_from_pipe_feed(pipe, &sd, pipe_to_file);
1008                }
1009                mutex_unlock(&inode->i_mutex);
1010        } while (ret > 0);
1011        splice_from_pipe_end(pipe, &sd);
1012
1013        pipe_unlock(pipe);
1014
1015        if (sd.num_spliced)
1016                ret = sd.num_spliced;
1017
1018        if (ret > 0) {
1019                unsigned long nr_pages;
1020                int err;
1021
1022                nr_pages = (ret + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
1023
1024                err = generic_write_sync(out, *ppos, ret);
1025                if (err)
1026                        ret = err;
1027                else
1028                        *ppos += ret;
1029                balance_dirty_pages_ratelimited_nr(mapping, nr_pages);
1030        }
1031
1032        return ret;
1033}
1034
1035EXPORT_SYMBOL(generic_file_splice_write);
1036
1037static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1038                          struct splice_desc *sd)
1039{
1040        int ret;
1041        void *data;
1042
1043        data = buf->ops->map(pipe, buf, 0);
1044        ret = kernel_write(sd->u.file, data + buf->offset, sd->len, sd->pos);
1045        buf->ops->unmap(pipe, buf, data);
1046
1047        return ret;
1048}
1049
1050static ssize_t default_file_splice_write(struct pipe_inode_info *pipe,
1051                                         struct file *out, loff_t *ppos,
1052                                         size_t len, unsigned int flags)
1053{
1054        ssize_t ret;
1055
1056        ret = splice_from_pipe(pipe, out, ppos, len, flags, write_pipe_buf);
1057        if (ret > 0)
1058                *ppos += ret;
1059
1060        return ret;
1061}
1062
1063/**
1064 * generic_splice_sendpage - splice data from a pipe to a socket
1065 * @pipe:       pipe to splice from
1066 * @out:        socket to write to
1067 * @ppos:       position in @out
1068 * @len:        number of bytes to splice
1069 * @flags:      splice modifier flags
1070 *
1071 * Description:
1072 *    Will send @len bytes from the pipe to a network socket. No data copying
1073 *    is involved.
1074 *
1075 */
1076ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
1077                                loff_t *ppos, size_t len, unsigned int flags)
1078{
1079        return splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
1080}
1081
1082EXPORT_SYMBOL(generic_splice_sendpage);
1083
1084/*
1085 * Attempt to initiate a splice from pipe to file.
1086 */
1087static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
1088                           loff_t *ppos, size_t len, unsigned int flags)
1089{
1090        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *,
1091                                loff_t *, size_t, unsigned int);
1092        int ret;
1093
1094        if (unlikely(!(out->f_mode & FMODE_WRITE)))
1095                return -EBADF;
1096
1097        if (unlikely(out->f_flags & O_APPEND))
1098                return -EINVAL;
1099
1100        ret = rw_verify_area(WRITE, out, ppos, len);
1101        if (unlikely(ret < 0))
1102                return ret;
1103
1104        if (out->f_op && out->f_op->splice_write)
1105                splice_write = out->f_op->splice_write;
1106        else
1107                splice_write = default_file_splice_write;
1108
1109        return splice_write(pipe, out, ppos, len, flags);
1110}
1111
1112/*
1113 * Attempt to initiate a splice from a file to a pipe.
1114 */
1115static long do_splice_to(struct file *in, loff_t *ppos,
1116                         struct pipe_inode_info *pipe, size_t len,
1117                         unsigned int flags)
1118{
1119        ssize_t (*splice_read)(struct file *, loff_t *,
1120                               struct pipe_inode_info *, size_t, unsigned int);
1121        int ret;
1122
1123        if (unlikely(!(in->f_mode & FMODE_READ)))
1124                return -EBADF;
1125
1126        ret = rw_verify_area(READ, in, ppos, len);
1127        if (unlikely(ret < 0))
1128                return ret;
1129
1130        if (in->f_op && in->f_op->splice_read)
1131                splice_read = in->f_op->splice_read;
1132        else
1133                splice_read = default_file_splice_read;
1134
1135        return splice_read(in, ppos, pipe, len, flags);
1136}
1137
1138/**
1139 * splice_direct_to_actor - splices data directly between two non-pipes
1140 * @in:         file to splice from
1141 * @sd:         actor information on where to splice to
1142 * @actor:      handles the data splicing
1143 *
1144 * Description:
1145 *    This is a special case helper to splice directly between two
1146 *    points, without requiring an explicit pipe. Internally an allocated
1147 *    pipe is cached in the process, and reused during the lifetime of
1148 *    that process.
1149 *
1150 */
1151ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
1152                               splice_direct_actor *actor)
1153{
1154        struct pipe_inode_info *pipe;
1155        long ret, bytes;
1156        umode_t i_mode;
1157        size_t len;
1158        int i, flags;
1159
1160        /*
1161         * We require the input being a regular file, as we don't want to
1162         * randomly drop data for eg socket -> socket splicing. Use the
1163         * piped splicing for that!
1164         */
1165        i_mode = in->f_path.dentry->d_inode->i_mode;
1166        if (unlikely(!S_ISREG(i_mode) && !S_ISBLK(i_mode)))
1167                return -EINVAL;
1168
1169        /*
1170         * neither in nor out is a pipe, setup an internal pipe attached to
1171         * 'out' and transfer the wanted data from 'in' to 'out' through that
1172         */
1173        pipe = current->splice_pipe;
1174        if (unlikely(!pipe)) {
1175                pipe = alloc_pipe_info(NULL);
1176                if (!pipe)
1177                        return -ENOMEM;
1178
1179                /*
1180                 * We don't have an immediate reader, but we'll read the stuff
1181                 * out of the pipe right after the splice_to_pipe(). So set
1182                 * PIPE_READERS appropriately.
1183                 */
1184                pipe->readers = 1;
1185
1186                current->splice_pipe = pipe;
1187        }
1188
1189        /*
1190         * Do the splice.
1191         */
1192        ret = 0;
1193        bytes = 0;
1194        len = sd->total_len;
1195        flags = sd->flags;
1196
1197        /*
1198         * Don't block on output, we have to drain the direct pipe.
1199         */
1200        sd->flags &= ~SPLICE_F_NONBLOCK;
1201
1202        while (len) {
1203                size_t read_len;
1204                loff_t pos = sd->pos, prev_pos = pos;
1205
1206                ret = do_splice_to(in, &pos, pipe, len, flags);
1207                if (unlikely(ret <= 0))
1208                        goto out_release;
1209
1210                read_len = ret;
1211                sd->total_len = read_len;
1212
1213                /*
1214                 * NOTE: nonblocking mode only applies to the input. We
1215                 * must not do the output in nonblocking mode as then we
1216                 * could get stuck data in the internal pipe:
1217                 */
1218                ret = actor(pipe, sd);
1219                if (unlikely(ret <= 0)) {
1220                        sd->pos = prev_pos;
1221                        goto out_release;
1222                }
1223
1224                bytes += ret;
1225                len -= ret;
1226                sd->pos = pos;
1227
1228                if (ret < read_len) {
1229                        sd->pos = prev_pos + ret;
1230                        goto out_release;
1231                }
1232        }
1233
1234done:
1235        pipe->nrbufs = pipe->curbuf = 0;
1236        file_accessed(in);
1237        return bytes;
1238
1239out_release:
1240        /*
1241         * If we did an incomplete transfer we must release
1242         * the pipe buffers in question:
1243         */
1244        for (i = 0; i < pipe->buffers; i++) {
1245                struct pipe_buffer *buf = pipe->bufs + i;
1246
1247                if (buf->ops) {
1248                        buf->ops->release(pipe, buf);
1249                        buf->ops = NULL;
1250                }
1251        }
1252
1253        if (!bytes)
1254                bytes = ret;
1255
1256        goto done;
1257}
1258EXPORT_SYMBOL(splice_direct_to_actor);
1259
1260static int direct_splice_actor(struct pipe_inode_info *pipe,
1261                               struct splice_desc *sd)
1262{
1263        struct file *file = sd->u.file;
1264
1265        return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
1266                              sd->flags);
1267}
1268
1269/**
1270 * do_splice_direct - splices data directly between two files
1271 * @in:         file to splice from
1272 * @ppos:       input file offset
1273 * @out:        file to splice to
1274 * @len:        number of bytes to splice
1275 * @flags:      splice modifier flags
1276 *
1277 * Description:
1278 *    For use by do_sendfile(). splice can easily emulate sendfile, but
1279 *    doing it in the application would incur an extra system call
1280 *    (splice in + splice out, as compared to just sendfile()). So this helper
1281 *    can splice directly through a process-private pipe.
1282 *
1283 */
1284long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
1285                      size_t len, unsigned int flags)
1286{
1287        struct splice_desc sd = {
1288                .len            = len,
1289                .total_len      = len,
1290                .flags          = flags,
1291                .pos            = *ppos,
1292                .u.file         = out,
1293        };
1294        long ret;
1295
1296        ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
1297        if (ret > 0)
1298                *ppos = sd.pos;
1299
1300        return ret;
1301}
1302
1303static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1304                               struct pipe_inode_info *opipe,
1305                               size_t len, unsigned int flags);
1306
1307/*
1308 * Determine where to splice to/from.
1309 */
1310static long do_splice(struct file *in, loff_t __user *off_in,
1311                      struct file *out, loff_t __user *off_out,
1312                      size_t len, unsigned int flags)
1313{
1314        struct pipe_inode_info *ipipe;
1315        struct pipe_inode_info *opipe;
1316        loff_t offset, *off;
1317        long ret;
1318
1319        ipipe = get_pipe_info(in);
1320        opipe = get_pipe_info(out);
1321
1322        if (ipipe && opipe) {
1323                if (off_in || off_out)
1324                        return -ESPIPE;
1325
1326                if (!(in->f_mode & FMODE_READ))
1327                        return -EBADF;
1328
1329                if (!(out->f_mode & FMODE_WRITE))
1330                        return -EBADF;
1331
1332                /* Splicing to self would be fun, but... */
1333                if (ipipe == opipe)
1334                        return -EINVAL;
1335
1336                return splice_pipe_to_pipe(ipipe, opipe, len, flags);
1337        }
1338
1339        if (ipipe) {
1340                if (off_in)
1341                        return -ESPIPE;
1342                if (off_out) {
1343                        if (!(out->f_mode & FMODE_PWRITE))
1344                                return -EINVAL;
1345                        if (copy_from_user(&offset, off_out, sizeof(loff_t)))
1346                                return -EFAULT;
1347                        off = &offset;
1348                } else
1349                        off = &out->f_pos;
1350
1351                ret = do_splice_from(ipipe, out, off, len, flags);
1352
1353                if (off_out && copy_to_user(off_out, off, sizeof(loff_t)))
1354                        ret = -EFAULT;
1355
1356                return ret;
1357        }
1358
1359        if (opipe) {
1360                if (off_out)
1361                        return -ESPIPE;
1362                if (off_in) {
1363                        if (!(in->f_mode & FMODE_PREAD))
1364                                return -EINVAL;
1365                        if (copy_from_user(&offset, off_in, sizeof(loff_t)))
1366                                return -EFAULT;
1367                        off = &offset;
1368                } else
1369                        off = &in->f_pos;
1370
1371                ret = do_splice_to(in, off, opipe, len, flags);
1372
1373                if (off_in && copy_to_user(off_in, off, sizeof(loff_t)))
1374                        ret = -EFAULT;
1375
1376                return ret;
1377        }
1378
1379        return -EINVAL;
1380}
1381
1382/*
1383 * Map an iov into an array of pages and offset/length tupples. With the
1384 * partial_page structure, we can map several non-contiguous ranges into
1385 * our ones pages[] map instead of splitting that operation into pieces.
1386 * Could easily be exported as a generic helper for other users, in which
1387 * case one would probably want to add a 'max_nr_pages' parameter as well.
1388 */
1389static int get_iovec_page_array(const struct iovec __user *iov,
1390                                unsigned int nr_vecs, struct page **pages,
1391                                struct partial_page *partial, int aligned,
1392                                unsigned int pipe_buffers)
1393{
1394        int buffers = 0, error = 0;
1395
1396        while (nr_vecs) {
1397                unsigned long off, npages;
1398                struct iovec entry;
1399                void __user *base;
1400                size_t len;
1401                int i;
1402
1403                error = -EFAULT;
1404                if (copy_from_user(&entry, iov, sizeof(entry)))
1405                        break;
1406
1407                base = entry.iov_base;
1408                len = entry.iov_len;
1409
1410                /*
1411                 * Sanity check this iovec. 0 read succeeds.
1412                 */
1413                error = 0;
1414                if (unlikely(!len))
1415                        break;
1416                error = -EFAULT;
1417                if (!access_ok(VERIFY_READ, base, len))
1418                        break;
1419
1420                /*
1421                 * Get this base offset and number of pages, then map
1422                 * in the user pages.
1423                 */
1424                off = (unsigned long) base & ~PAGE_MASK;
1425
1426                /*
1427                 * If asked for alignment, the offset must be zero and the
1428                 * length a multiple of the PAGE_SIZE.
1429                 */
1430                error = -EINVAL;
1431                if (aligned && (off || len & ~PAGE_MASK))
1432                        break;
1433
1434                npages = (off + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
1435                if (npages > pipe_buffers - buffers)
1436                        npages = pipe_buffers - buffers;
1437
1438                error = get_user_pages_fast((unsigned long)base, npages,
1439                                        0, &pages[buffers]);
1440
1441                if (unlikely(error <= 0))
1442                        break;
1443
1444                /*
1445                 * Fill this contiguous range into the partial page map.
1446                 */
1447                for (i = 0; i < error; i++) {
1448                        const int plen = min_t(size_t, len, PAGE_SIZE - off);
1449
1450                        partial[buffers].offset = off;
1451                        partial[buffers].len = plen;
1452
1453                        off = 0;
1454                        len -= plen;
1455                        buffers++;
1456                }
1457
1458                /*
1459                 * We didn't complete this iov, stop here since it probably
1460                 * means we have to move some of this into a pipe to
1461                 * be able to continue.
1462                 */
1463                if (len)
1464                        break;
1465
1466                /*
1467                 * Don't continue if we mapped fewer pages than we asked for,
1468                 * or if we mapped the max number of pages that we have
1469                 * room for.
1470                 */
1471                if (error < npages || buffers == pipe_buffers)
1472                        break;
1473
1474                nr_vecs--;
1475                iov++;
1476        }
1477
1478        if (buffers)
1479                return buffers;
1480
1481        return error;
1482}
1483
1484static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
1485                        struct splice_desc *sd)
1486{
1487        char *src;
1488        int ret;
1489
1490        /*
1491         * See if we can use the atomic maps, by prefaulting in the
1492         * pages and doing an atomic copy
1493         */
1494        if (!fault_in_pages_writeable(sd->u.userptr, sd->len)) {
1495                src = buf->ops->map(pipe, buf, 1);
1496                ret = __copy_to_user_inatomic(sd->u.userptr, src + buf->offset,
1497                                                        sd->len);
1498                buf->ops->unmap(pipe, buf, src);
1499                if (!ret) {
1500                        ret = sd->len;
1501                        goto out;
1502                }
1503        }
1504
1505        /*
1506         * No dice, use slow non-atomic map and copy
1507         */
1508        src = buf->ops->map(pipe, buf, 0);
1509
1510        ret = sd->len;
1511        if (copy_to_user(sd->u.userptr, src + buf->offset, sd->len))
1512                ret = -EFAULT;
1513
1514        buf->ops->unmap(pipe, buf, src);
1515out:
1516        if (ret > 0)
1517                sd->u.userptr += ret;
1518        return ret;
1519}
1520
1521/*
1522 * For lack of a better implementation, implement vmsplice() to userspace
1523 * as a simple copy of the pipes pages to the user iov.
1524 */
1525static long vmsplice_to_user(struct file *file, const struct iovec __user *iov,
1526                             unsigned long nr_segs, unsigned int flags)
1527{
1528        struct pipe_inode_info *pipe;
1529        struct splice_desc sd;
1530        ssize_t size;
1531        int error;
1532        long ret;
1533
1534        pipe = get_pipe_info(file);
1535        if (!pipe)
1536                return -EBADF;
1537
1538        pipe_lock(pipe);
1539
1540        error = ret = 0;
1541        while (nr_segs) {
1542                void __user *base;
1543                size_t len;
1544
1545                /*
1546                 * Get user address base and length for this iovec.
1547                 */
1548                error = get_user(base, &iov->iov_base);
1549                if (unlikely(error))
1550                        break;
1551                error = get_user(len, &iov->iov_len);
1552                if (unlikely(error))
1553                        break;
1554
1555                /*
1556                 * Sanity check this iovec. 0 read succeeds.
1557                 */
1558                if (unlikely(!len))
1559                        break;
1560                if (unlikely(!base)) {
1561                        error = -EFAULT;
1562                        break;
1563                }
1564
1565                if (unlikely(!access_ok(VERIFY_WRITE, base, len))) {
1566                        error = -EFAULT;
1567                        break;
1568                }
1569
1570                sd.len = 0;
1571                sd.total_len = len;
1572                sd.flags = flags;
1573                sd.u.userptr = base;
1574                sd.pos = 0;
1575
1576                size = __splice_from_pipe(pipe, &sd, pipe_to_user);
1577                if (size < 0) {
1578                        if (!ret)
1579                                ret = size;
1580
1581                        break;
1582                }
1583
1584                ret += size;
1585
1586                if (size < len)
1587                        break;
1588
1589                nr_segs--;
1590                iov++;
1591        }
1592
1593        pipe_unlock(pipe);
1594
1595        if (!ret)
1596                ret = error;
1597
1598        return ret;
1599}
1600
1601/*
1602 * vmsplice splices a user address range into a pipe. It can be thought of
1603 * as splice-from-memory, where the regular splice is splice-from-file (or
1604 * to file). In both cases the output is a pipe, naturally.
1605 */
1606static long vmsplice_to_pipe(struct file *file, const struct iovec __user *iov,
1607                             unsigned long nr_segs, unsigned int flags)
1608{
1609        struct pipe_inode_info *pipe;
1610        struct page *pages[PIPE_DEF_BUFFERS];
1611        struct partial_page partial[PIPE_DEF_BUFFERS];
1612        struct splice_pipe_desc spd = {
1613                .pages = pages,
1614                .partial = partial,
1615                .flags = flags,
1616                .ops = &user_page_pipe_buf_ops,
1617                .spd_release = spd_release_page,
1618        };
1619        long ret;
1620
1621        pipe = get_pipe_info(file);
1622        if (!pipe)
1623                return -EBADF;
1624
1625        if (splice_grow_spd(pipe, &spd))
1626                return -ENOMEM;
1627
1628        spd.nr_pages = get_iovec_page_array(iov, nr_segs, spd.pages,
1629                                            spd.partial, flags & SPLICE_F_GIFT,
1630                                            pipe->buffers);
1631        if (spd.nr_pages <= 0)
1632                ret = spd.nr_pages;
1633        else
1634                ret = splice_to_pipe(pipe, &spd);
1635
1636        splice_shrink_spd(pipe, &spd);
1637        return ret;
1638}
1639
1640/*
1641 * Note that vmsplice only really supports true splicing _from_ user memory
1642 * to a pipe, not the other way around. Splicing from user memory is a simple
1643 * operation that can be supported without any funky alignment restrictions
1644 * or nasty vm tricks. We simply map in the user memory and fill them into
1645 * a pipe. The reverse isn't quite as easy, though. There are two possible
1646 * solutions for that:
1647 *
1648 *      - memcpy() the data internally, at which point we might as well just
1649 *        do a regular read() on the buffer anyway.
1650 *      - Lots of nasty vm tricks, that are neither fast nor flexible (it
1651 *        has restriction limitations on both ends of the pipe).
1652 *
1653 * Currently we punt and implement it as a normal copy, see pipe_to_user().
1654 *
1655 */
1656SYSCALL_DEFINE4(vmsplice, int, fd, const struct iovec __user *, iov,
1657                unsigned long, nr_segs, unsigned int, flags)
1658{
1659        struct file *file;
1660        long error;
1661        int fput;
1662
1663        if (unlikely(nr_segs > UIO_MAXIOV))
1664                return -EINVAL;
1665        else if (unlikely(!nr_segs))
1666                return 0;
1667
1668        error = -EBADF;
1669        file = fget_light(fd, &fput);
1670        if (file) {
1671                if (file->f_mode & FMODE_WRITE)
1672                        error = vmsplice_to_pipe(file, iov, nr_segs, flags);
1673                else if (file->f_mode & FMODE_READ)
1674                        error = vmsplice_to_user(file, iov, nr_segs, flags);
1675
1676                fput_light(file, fput);
1677        }
1678
1679        return error;
1680}
1681
1682SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
1683                int, fd_out, loff_t __user *, off_out,
1684                size_t, len, unsigned int, flags)
1685{
1686        long error;
1687        struct file *in, *out;
1688        int fput_in, fput_out;
1689
1690        if (unlikely(!len))
1691                return 0;
1692
1693        error = -EBADF;
1694        in = fget_light(fd_in, &fput_in);
1695        if (in) {
1696                if (in->f_mode & FMODE_READ) {
1697                        out = fget_light(fd_out, &fput_out);
1698                        if (out) {
1699                                if (out->f_mode & FMODE_WRITE)
1700                                        error = do_splice(in, off_in,
1701                                                          out, off_out,
1702                                                          len, flags);
1703                                fput_light(out, fput_out);
1704                        }
1705                }
1706
1707                fput_light(in, fput_in);
1708        }
1709
1710        return error;
1711}
1712
1713/*
1714 * Make sure there's data to read. Wait for input if we can, otherwise
1715 * return an appropriate error.
1716 */
1717static int ipipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1718{
1719        int ret;
1720
1721        /*
1722         * Check ->nrbufs without the inode lock first. This function
1723         * is speculative anyways, so missing one is ok.
1724         */
1725        if (pipe->nrbufs)
1726                return 0;
1727
1728        ret = 0;
1729        pipe_lock(pipe);
1730
1731        while (!pipe->nrbufs) {
1732                if (signal_pending(current)) {
1733                        ret = -ERESTARTSYS;
1734                        break;
1735                }
1736                if (!pipe->writers)
1737                        break;
1738                if (!pipe->waiting_writers) {
1739                        if (flags & SPLICE_F_NONBLOCK) {
1740                                ret = -EAGAIN;
1741                                break;
1742                        }
1743                }
1744                pipe_wait(pipe);
1745        }
1746
1747        pipe_unlock(pipe);
1748        return ret;
1749}
1750
1751/*
1752 * Make sure there's writeable room. Wait for room if we can, otherwise
1753 * return an appropriate error.
1754 */
1755static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
1756{
1757        int ret;
1758
1759        /*
1760         * Check ->nrbufs without the inode lock first. This function
1761         * is speculative anyways, so missing one is ok.
1762         */
1763        if (pipe->nrbufs < pipe->buffers)
1764                return 0;
1765
1766        ret = 0;
1767        pipe_lock(pipe);
1768
1769        while (pipe->nrbufs >= pipe->buffers) {
1770                if (!pipe->readers) {
1771                        send_sig(SIGPIPE, current, 0);
1772                        ret = -EPIPE;
1773                        break;
1774                }
1775                if (flags & SPLICE_F_NONBLOCK) {
1776                        ret = -EAGAIN;
1777                        break;
1778                }
1779                if (signal_pending(current)) {
1780                        ret = -ERESTARTSYS;
1781                        break;
1782                }
1783                pipe->waiting_writers++;
1784                pipe_wait(pipe);
1785                pipe->waiting_writers--;
1786        }
1787
1788        pipe_unlock(pipe);
1789        return ret;
1790}
1791
1792/*
1793 * Splice contents of ipipe to opipe.
1794 */
1795static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
1796                               struct pipe_inode_info *opipe,
1797                               size_t len, unsigned int flags)
1798{
1799        struct pipe_buffer *ibuf, *obuf;
1800        int ret = 0, nbuf;
1801        bool input_wakeup = false;
1802
1803
1804retry:
1805        ret = ipipe_prep(ipipe, flags);
1806        if (ret)
1807                return ret;
1808
1809        ret = opipe_prep(opipe, flags);
1810        if (ret)
1811                return ret;
1812
1813        /*
1814         * Potential ABBA deadlock, work around it by ordering lock
1815         * grabbing by pipe info address. Otherwise two different processes
1816         * could deadlock (one doing tee from A -> B, the other from B -> A).
1817         */
1818        pipe_double_lock(ipipe, opipe);
1819
1820        do {
1821                if (!opipe->readers) {
1822                        send_sig(SIGPIPE, current, 0);
1823                        if (!ret)
1824                                ret = -EPIPE;
1825                        break;
1826                }
1827
1828                if (!ipipe->nrbufs && !ipipe->writers)
1829                        break;
1830
1831                /*
1832                 * Cannot make any progress, because either the input
1833                 * pipe is empty or the output pipe is full.
1834                 */
1835                if (!ipipe->nrbufs || opipe->nrbufs >= opipe->buffers) {
1836                        /* Already processed some buffers, break */
1837                        if (ret)
1838                                break;
1839
1840                        if (flags & SPLICE_F_NONBLOCK) {
1841                                ret = -EAGAIN;
1842                                break;
1843                        }
1844
1845                        /*
1846                         * We raced with another reader/writer and haven't
1847                         * managed to process any buffers.  A zero return
1848                         * value means EOF, so retry instead.
1849                         */
1850                        pipe_unlock(ipipe);
1851                        pipe_unlock(opipe);
1852                        goto retry;
1853                }
1854
1855                ibuf = ipipe->bufs + ipipe->curbuf;
1856                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1857                obuf = opipe->bufs + nbuf;
1858
1859                if (len >= ibuf->len) {
1860                        /*
1861                         * Simply move the whole buffer from ipipe to opipe
1862                         */
1863                        *obuf = *ibuf;
1864                        ibuf->ops = NULL;
1865                        opipe->nrbufs++;
1866                        ipipe->curbuf = (ipipe->curbuf + 1) & (ipipe->buffers - 1);
1867                        ipipe->nrbufs--;
1868                        input_wakeup = true;
1869                } else {
1870                        /*
1871                         * Get a reference to this pipe buffer,
1872                         * so we can copy the contents over.
1873                         */
1874                        ibuf->ops->get(ipipe, ibuf);
1875                        *obuf = *ibuf;
1876
1877                        /*
1878                         * Don't inherit the gift flag, we need to
1879                         * prevent multiple steals of this page.
1880                         */
1881                        obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1882
1883                        obuf->len = len;
1884                        opipe->nrbufs++;
1885                        ibuf->offset += obuf->len;
1886                        ibuf->len -= obuf->len;
1887                }
1888                ret += obuf->len;
1889                len -= obuf->len;
1890        } while (len);
1891
1892        pipe_unlock(ipipe);
1893        pipe_unlock(opipe);
1894
1895        /*
1896         * If we put data in the output pipe, wakeup any potential readers.
1897         */
1898        if (ret > 0)
1899                wakeup_pipe_readers(opipe);
1900
1901        if (input_wakeup)
1902                wakeup_pipe_writers(ipipe);
1903
1904        return ret;
1905}
1906
1907/*
1908 * Link contents of ipipe to opipe.
1909 */
1910static int link_pipe(struct pipe_inode_info *ipipe,
1911                     struct pipe_inode_info *opipe,
1912                     size_t len, unsigned int flags)
1913{
1914        struct pipe_buffer *ibuf, *obuf;
1915        int ret = 0, i = 0, nbuf;
1916
1917        /*
1918         * Potential ABBA deadlock, work around it by ordering lock
1919         * grabbing by pipe info address. Otherwise two different processes
1920         * could deadlock (one doing tee from A -> B, the other from B -> A).
1921         */
1922        pipe_double_lock(ipipe, opipe);
1923
1924        do {
1925                if (!opipe->readers) {
1926                        send_sig(SIGPIPE, current, 0);
1927                        if (!ret)
1928                                ret = -EPIPE;
1929                        break;
1930                }
1931
1932                /*
1933                 * If we have iterated all input buffers or ran out of
1934                 * output room, break.
1935                 */
1936                if (i >= ipipe->nrbufs || opipe->nrbufs >= opipe->buffers)
1937                        break;
1938
1939                ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (ipipe->buffers-1));
1940                nbuf = (opipe->curbuf + opipe->nrbufs) & (opipe->buffers - 1);
1941
1942                /*
1943                 * Get a reference to this pipe buffer,
1944                 * so we can copy the contents over.
1945                 */
1946                ibuf->ops->get(ipipe, ibuf);
1947
1948                obuf = opipe->bufs + nbuf;
1949                *obuf = *ibuf;
1950
1951                /*
1952                 * Don't inherit the gift flag, we need to
1953                 * prevent multiple steals of this page.
1954                 */
1955                obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
1956
1957                if (obuf->len > len)
1958                        obuf->len = len;
1959
1960                opipe->nrbufs++;
1961                ret += obuf->len;
1962                len -= obuf->len;
1963                i++;
1964        } while (len);
1965
1966        /*
1967         * return EAGAIN if we have the potential of some data in the
1968         * future, otherwise just return 0
1969         */
1970        if (!ret && ipipe->waiting_writers && (flags & SPLICE_F_NONBLOCK))
1971                ret = -EAGAIN;
1972
1973        pipe_unlock(ipipe);
1974        pipe_unlock(opipe);
1975
1976        /*
1977         * If we put data in the output pipe, wakeup any potential readers.
1978         */
1979        if (ret > 0)
1980                wakeup_pipe_readers(opipe);
1981
1982        return ret;
1983}
1984
1985/*
1986 * This is a tee(1) implementation that works on pipes. It doesn't copy
1987 * any data, it simply references the 'in' pages on the 'out' pipe.
1988 * The 'flags' used are the SPLICE_F_* variants, currently the only
1989 * applicable one is SPLICE_F_NONBLOCK.
1990 */
1991static long do_tee(struct file *in, struct file *out, size_t len,
1992                   unsigned int flags)
1993{
1994        struct pipe_inode_info *ipipe = get_pipe_info(in);
1995        struct pipe_inode_info *opipe = get_pipe_info(out);
1996        int ret = -EINVAL;
1997
1998        /*
1999         * Duplicate the contents of ipipe to opipe without actually
2000         * copying the data.
2001         */
2002        if (ipipe && opipe && ipipe != opipe) {
2003                /*
2004                 * Keep going, unless we encounter an error. The ipipe/opipe
2005                 * ordering doesn't really matter.
2006                 */
2007                ret = ipipe_prep(ipipe, flags);
2008                if (!ret) {
2009                        ret = opipe_prep(opipe, flags);
2010                        if (!ret)
2011                                ret = link_pipe(ipipe, opipe, len, flags);
2012                }
2013        }
2014
2015        return ret;
2016}
2017
2018SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
2019{
2020        struct file *in;
2021        int error, fput_in;
2022
2023        if (unlikely(!len))
2024                return 0;
2025
2026        error = -EBADF;
2027        in = fget_light(fdin, &fput_in);
2028        if (in) {
2029                if (in->f_mode & FMODE_READ) {
2030                        int fput_out;
2031                        struct file *out = fget_light(fdout, &fput_out);
2032
2033                        if (out) {
2034                                if (out->f_mode & FMODE_WRITE)
2035                                        error = do_tee(in, out, len, flags);
2036                                fput_light(out, fput_out);
2037                        }
2038                }
2039                fput_light(in, fput_in);
2040        }
2041
2042        return error;
2043}
2044